Sheet drying apparatus



Aug. 27, 1957 Filed Nov. 20, 1953 2 Sheets-Sheet 1 .Fig. I

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10 l2 I6 I8 20 INVENTOR.

ALEXIS E. USHAKOFF AT TOR NEYS' Aug. 27, 1957 A. E. USHAKOFF 2,803,889

SHEETIDRYING APPARATUS Filed NOV. 20, 1953 2 Sheets-Sheet 2 Fig.2

ILJEJJJ 1 F it]. 3 INVENTOR.

ALEXIS E USHAKOFF ATTORNEYS 2,803,889 Patented Aug. 27, 1957 fine SHEET DRYING APPARATUS Alexis E. Ushakoflt, Beverly, Mass., assignor to Secotan, Inc, Somerville, Mass., a corporation of Massachusetts Application November 20, 1953, Serial No. 393,329

2 Claims. (Cl. 34-143) The present invention consists in apparatus for the rapid drying of porous sheet materials under controlled conditions of gas pressure, temperature and uniform surface pressure.

In the apparatus of this invention drying is carried out between a pair of heated surfaces exterting uniform surface pressure on the sheet, while the gas pressure within the sheet is independently controlled, and the vapors removed are collected for recovery. The sheet is thus secured flat during drying whereby wrinkles or creases are ironed out and shrinkage is minimized, and the application of heat is at a substantially uniform rate. The apparatus is particularly useful for removing organic solvents from sheets of non-uniform thickness, in providing uniform surface pressure, uniform heating, controlled gas pressure and vapor recovery. In addition, the appa ratus is so constructed that the sheets to be dried may be introduced and removed rapidly while the solvent vapors driven from them are channeled into the recovery system with negligible escape into the atmosphere of the surrounding working space.

In general, the apparatus consists of a foraminous heated platen, a heating surface retractably mounted opposite one side of the platen for motion toward or from the platen, and a pan forming a manifold region secured about its edges to the other side of the platen and connecting with a vapor recovery conduit. In the preferred embodiment the heating surface consists of an extended inflatable diaphragm mounted opposite the one side of the platen, whereby the application of a hot fluid heats the diaphrgam while forcing it toward the platen. With the sheet to be dried between the platen and the diaphragm, uniform pressure and uniform heating are applied while the sheet is pressed and secured flat, and the manifold region on the other side of the foraminous platen provides for both controlled gas pressure within the sheet and solvent recovery.

The heated platen is preferably formed of a good heat conducting material to assure a substantially uniform temperature at its heating surface, suitable materials being steel, aluminum, copper, brass, or other fabricating metals. Heating may be by means of steam, in which case the platen is cored, or by other well known eX- pedients.

The diaphragm is suitably a flexible sheet, preferably somewhat elastic, of heat resistant material having reasonable thermal conductivity, and should be selected to resist the action of any chemicals encountered during drying. Suitable materials include natural rubber and such synthetic rubbers as butyl rubber, butadiene-styrene copolymers, butadiene-acrylonitrite copolymers, polychloroprene and silicone rubber, as well as other flexible and elastic synthetic organic resins having the above characteristics.

The diaphrgam may consist of a sheet of these materials with or without a reinforcing backing. Where a substantially elastic diaphragm is desired an unbacked sheet of natural or synthetic rubber is suitable, but where greater strength is desired a backing of such heat resistant fabrics as glass cloth, asbestos cloth or screen or cloth of heat resistant synthetic organic resins, is preferably included to reinforce the sheet.

This invention will best be understood from the following detailed description of preferred embodiments wherein reference is made to the drawings in which:

Fig. 1 is an elevational view in cross-section of one embodiment of this invention,

Fig. 2 is an elevational view in cross-section showing alternative construction of the inflatable diaphragm, Fig. 3 is a view taken at section 3-3 of Fig. 2, and

Fig. 4 is a perspective view of a section of a tray for supporting a sheet in the apparatus.

In the embodiment shown in Fig. 1, the foraminous platen It) is formed of a pair of spaced parallel plates 12 and 14, secured together at their edges, and correspondingly perforated and connected by tube sections 16 providing continuous channels through the platen. A heating conduit 18 and a drain conduit 20 enter the space between the plates 12 and 14- and provide means for supplying and withdrawing a heating fluid to the platen.

Mounted on bolts 22 over the platen it is a pressure head plate 24 to the edges of which are mounted the edges of the diaphragm 26, conveniently by clamping the diaphragm between the head plate 2 and a rim 28. An inflating conduit 3t enters the space between the diaphragm 26 and the head plate 24 through the latter, through which also enters a bleeder pipe 32 connected to a flexible drain tube 34 resting at its lower end on the diaphragm.

Mounted beneath the platen it to the lower plate 12, is a pan 16 defining beneath the lower plate a manifold region 38 into which connect the lower ends of the tube section 16, and a recovery conduit 49 connected through the botto .1 of the pan.

In this embodiment the diaphragm 26 is preferably elastic since it is rigidly supported at its edges for inflation downward, and must, therefore, be stretched for best results.

Where it is desired to utilize an inelastic diaphragm the diaphragm supporting structure shown in Figs. 2 and 3 is recommended. In that embodiment the diaphragm is formed as an inflatable flat bag 43 having a lower ply 50 secured at its edges, as by stitching 52, to an upper ply 54, and the latter is provided with a hole secured at its edges about the inflating conduit 3% Mounted over the upper ply 54 is a backing plate 56, against which the upper ply in inflated as the lower ply inflates downward. Springs 58 secured to the corner bolts 22 supporting the backing plate 56 hold the bag flat while yielding to permit horizontal contraction during inflation.

For supporting the sheet being dried a porous, preferably smooth surfaced tray 59, such as that shown in Fig. 4 is utilized. This consists of a fine mesh, e. g. 40- mesh, wire screen hit on which is supported a smoothsurfaced porous ply 62 of for instance, paper impregnated, strengthened and wet-proofed with a synthetic-organic film-forming resin such as nylon. The edges of the screen and porous ply are preferably clamped together in a rim member 64.

The apparatus is installed for operation by connecting the platen heating conduit 18 and the inflating conduit 30 to a source of hot fluid such as saturated steam, and the bleeder pipe 32 and platen drain conduit 20 to a drain for carrying off condensate. The recovery conduit 40 is connected to a recovery system if valuable solvents are to be removed from the sheet to be dried, or is vented to the atmosphere if the liquid to: be removed is not to be recovered. A pressure regulating device, such as a vacuum pump, may be connected with the recovery conduit if drying at other than atmospheric pressure is desired.

For operation, the sheet to be dried is placed flat on the tray 59 which is in turn placed on the heated platen beneath the diaphragm. Steam is then admitted through the inflating conduit 30 to cause the diaphragm to inflate downward against the sheet and exert a uniform pressure over its surface. Heating of the sheet then proceeds rapidly from the top and bottom surfaces, while the pressure in the sheet is maintained at any desired value as determined by the pressure maintained in the recovery conduit 40. Control over the gas pressure in the skin is particularly advantageous where high boiling liquids are to be removed, since a low pressure may be maintained under which the liquid may be removed at low temperature.

Condensate formed on the diaphragm is drained through the flexible tube 34 and bleeder tube 32 While condensate formed in the platen is removed through the platen drain conduit 20. Desirably both the bleeder tube 32 and drain conduit are valved to prevent excessive escape of steam.

In addition to its function in heating the sheet, the diaphragm also extends downwardly to contact the upper surface of the platen, thus forming about the sheet an enclosed region communicating solely with the manifold region 38 and the recovery conduit 40. This feature permits solvent recovery without loss to the atmosphere surrounding the apparatus, and without dilution by incoming air.

It will be understood that the embodiments of this invention described above are illustrative thereof, and that modification readily occurring to those skilled in the art may be made without departing from the scope of the invention. It is contemplated for instance, that for many applications, especially where sheets of uniform thickness are to be dried, the upper heating surface may be a flat and rigid heated plate retractably mounted over the heated foraminous platen. Such a construction would contain the advantages of independent gas-pressure control and vapor recovery provided by the foraminous manifolded platen.

A particularly useful application of this invention is in the drying of leather, especially leather tanned in organic liquid systems. Leather is seldom of uniform thickness,

and if wet with organic liquids, these should be recovered. The pp ratus of this inventi n provides niform P sing of the leather, rapid and uniform heating, controlled gas pressure and vapor recovery, and in addition secures the leather during drying against shrinkage or wrinkling.

A further useful feature of this invention in the drying of leather is the utilization of an embossed surface on the tray 59 whereby a reversely embossed pattern may be applied to the surface of the leather.

The control over the gas pressure afforded by this invention is also especially advantageous in the drying of leather in permitting drying at low temperature.

Having thus disclosed my invention and described in detail preferred embodiments thereof, I claim and desire to secure by Letters Patent;

1. Sheet drying apparatus comprising a foraminous horizontal platen, means for heating said platen, an extended flexible diaphragm mounted over said platen in spaced relationship thereto, the space between the diaphragm and platen permitting the edgewise insertion of a sheet to be dried, means for inflating said diaphragm to extend it downwardly toward said platen, and a flexible conduit resting at one end on said diaphragm serving as a drain for condensate collecting on said diaphragm.

2. Sheet drying apparatus comprising a foraminous horizontal platen, means for heating said platen, enclosing means defining a manifold region on the bottom of said platen, an extended diaphragm mounted over said platen in spaced relation thereto, the space between the diaphragm and platen permitting the edgewise insertion of a sheet to be dried, means for inflating said diaphragm to extend it toward said platen into contact with a sheet thereon, and a flexible drain conduit resting at one end on said diaphragm serving as a drain for condensate collecting on said diaphragm.

References Cited in the file of this patent UNITED STATES PATENTS 173,083 Swartz Feb. 1, 1876 2,095,118 Basler Oct. 5, 1937 2,151,880 Wiederkehr Mar. 28, 1939 2,524,932 Schulman Oct. 10, 1950 2,646,105 Langer July 21, 1953 2,661,543 Tyndall et al Dec. 8, 1953 2,725,091 Miner -et a1. Nov. 29, 1955 er" w 

